1. Field of the Invention
The present invention relates to a sheet conveying apparatus for an electrophotographic copying machine, a printing press, a printer, an automatic document feeder (ADF) or the like, and more specifically to a paper jam treatment technique.
2. Related Background Art
In the past, the most efficient means for a paper jamming treatment incidental to the sheet conveyance in a sheet conveying device, such as an electrophotographic copying machine and a printer, was for the subsequent sheet not to be conveyed until a sheet of copying paper had been completely ejected from the apparatus, so that the jam treatment could be completed if only the jammed sheet was removed. Such a paper conveying system is applicable to a low-speed small sized machine, but is not suitable for a high-speed large sized machine. An improved sheet conveying apparatus was therefore employed in which the interval of sheet conveyance was set as short as possible in order to speed up sheet conveyance with regard to the high-speed large sized machine. Such sheet conveying apparatus could be, for example, utilized for an image forming apparatus to obtain a high-productivity per hour.
On the other hand, due to development of multiple functions such as color copy and multiple copy, the distance of sheet conveyance was liable to be elongated with the result that the number of sheets resting on the conveyance path was increased in the above-mentioned image forming apparatus.
There has also been proposed a sheet conveying apparatus which is adapted for the automatization of collation or finishing process by connecting an output sheet processing apparatus such as a sorter or a finisher therewith as well as aforementioned development of speed-up and multi-function.
However, in the prior art described above, the entire conveying operation of the sheet conveying apparatus including output sheet processing apparatus is stopped immediately after paper jamming occurs in, for example, the output sheet processing apparatus. As a result, the sheets being conveyed remained on the conveyance path, so that an operator had to remove the remaining sheets as well as the jammed sheet in the output sheet processing apparatus by inspecting the respective portions of the conveyance path, resulting in a poor jamming treatment.
Specifically in the electrophotographic copying machine, the operator's hands were soiled with unfixed toner when removing the jammed sheet between a photosensitive body of image forming portion and a fixing device.
Furthermore, as the sheet supplying portion tended to have a further complicated and elongated path for sheet conveyance, there were more points to be inspected for remaining sheets. Accordingly the inspection and removal of the jammed paper was a time-consuming, and a lot of time was required for jam return, in other words, normalization of the apparatus.
Moreover, some sheet conveyance apparatus used in an electrophotographic copying machine, etc., functioned to automatically eject the sheets on the conveyance path from the apparatus without removing the sheets on the path one by one providing the jammed sheet was treated (referred to as autoclear function). However, the sheet which was stopped on the path in the middle of image forming obtained a defective image, thereby being discharged as a mere miss sheet. In consequence, there was a drawback that aforesaid miss sheets and normal sheets were mingled to disorder pages of the sheets.